When mutations are passed to offspring and confer a selective advantage to them, the genome of the population changes. This is an evolutionary mechanism.
You have chosen to re-label evolutionary mechanisms as “built-in flexibility.” But whatever you want to call the mechanism, it has been observed to cause many cases of speciation both in lab and in the wild.
Recombination is a form of mutation that results in DNA changes that can be passed to offspring and selected for by environmental factors. In other words, it is an evolutionary mechanism. Sure, call it a built-in-mechanism if you want–in which case you are saying that evolutionary mechanisms are built-in. And I would agree.